GENEVA (Reuters) - Australia and Hong Kong have joined
North America and parts of Europe in reporting seasonal
influenza viruses with increased resistance to the antiviral
drug Tamiflu, the World Health Organization said on Thursday.

The WHO said that it was still gathering global data about
"an increased number of (seasonal) H1N1 viruses with resistance
to oseltamivir" following the first reports which emerged in
Europe in late January.

Oseltamivir is the generic name for Tamiflu, made by
Switzerland's Roche Holding AG and Gilead Sciences Inc of the
United States, which governments worldwide have been
stockpiling as a first line of defense in case the bird flu
virus sparks a human influenza pandemic.

The mutated H1N1 showing resistance is a sub-type of
ordinary influenza A, different from the H5N1 virus which
causes bird flu. But the resistance to Tamiflu has raised
questions about its potential effectiveness in a deadly bird
flu pandemic.

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Spokeswoman Sari Setiogi said that for now the WHO was not
changing its recommendation that Tamiflu be used to treat
seasonal flu.

"We still expect to see more testing be done," she said.

In Hong Kong, 5 of 67 samples of the H1N1 virus tested, or
7 percent, showed resistance to Tamiflu, according to a WHO
table. In Australia the rate was 2 out of 36 samples, or 6
percent.

In Japan, where Tamiflu is widely prescribed for seasonal
flu, none of the 71 samples tested showed resistance, WHO said.

A week ago, the WHO reported that the main seasonal virus
circulating in both Canada and the United States showed
"elevated resistance" to Tamiflu. These rates are 6 percent and
8 percent, respectively, according to the WHO's latest figures.

A preliminary survey issued by the European Centre for
Disease Control (ECDC) last month said that of 148 samples of
influenza A virus isolated from 10 European countries during
November and December, 19 showed signs of resistance to
Tamiflu.